RAF-1 kinase, CEP290, photoreceptor degeneration & ciliopathies

Nov 16, 2015
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Murga-Zamalloa CA, Ghosh AK, Patil SB, Reed NA, Chan LS, Davuluri S, Peranen J, Hurd TW, Rachel RA, Khanna H. Accumulation of RAF-1 kinase inhibitory protein (RKIP) is associated with CEP290-mediated photoreceptor degeneration in ciliopathies. J. Biol. Chem. 2011;[epub ahead of print] jbc.M111.237560. doi:10.1074/jbc.M111.237560
 
Nov 16, 2015
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Hello all,
do you think photoreceptor degeneration caused by CEP290 by this protein’s accumulation can be reversed, i.e. normal cilia can be formed and outer segments rebuilt when the right amounts of proteins is restored? I know that outer segments are shed every 10 days in normal photoreceptors, so that makes me hope...I have LCA caused by CEP290.
Thanks for any feedback

Fran – Italy
 
Nov 16, 2015
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Hi Fran,



I am not an eye specialist; hopefully someone with more relevent experience can chime in. The paper I cited above finishes with the statement "RKIP and other such proteins also provide possible therapeutic targets in the management of retinal and other neurodegenerative disorders. Additional comprehensive analysis of ciliary function of RKIP should allow development of optimal therapeutic modalities." It appears the authors are considering RKIP as a potentially useful target for therapeutic inhibition. They inhibited the translation of cep290 with a Morpholino oligo, but did not do the same sort of knockdown for RKIP. It would be interesting to see results of a double-knockdown of cep290 and RKIP; if the pathogenic outcome of loss of cep290 is entirely due to RKIP overexpression, the double knockdown might rescue the wild-type condition. The zebrafish embryo work was done in the context of a developing embryo instead of in an adult eye. Even if a double knockdown during development makes an eye with wild-type ciliary distribution, that is no guarantee that knocking down RKIP in an adult would result in ciliary rearrangement or ciliogenesis. However, this is potentially a worthwhile lead for therapeutic development.
 
Nov 16, 2015
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Jon, thank you so much. I know researchers are testing gene therapy for CEP290 in animals. Would this be a different approach from gene therapy? I mean, can you down regulate proteins without actually injecting the healthy gene with viral vectors?
Thanks so much for your time
Fran
 
Nov 16, 2015
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Hi Fran,



Morpholino antisense technology, as used in the paper I originally cited when starting this thread, makes no changes in the DNA, likely simplifying the process of drug approval. Instead, these synthetic compounds (analogs of nucleic acids) bind to complementary RNA and can interrupt the processes that RNA normally participates in, for example preventing translation of an mRNA or modifying the splicing of a pre-mRNA. AVI BioPharma Inc. has been conducting clinical testing of Morpholinos for a range of viral and genetic diseases, most recently Duchenne muscular dystrophy and influenza. No viral vector is involved in delivering Morpholinos, but their delivery into cells in vivo can be challenging as they do not readily cross the plasma membrane of most cells. Techniques like microinjection, localized electroporation and covalently-coupled delivery moieties have been used to deliver Morpholinos in vivo. They are a standard method of gene knockdown in developmental biology; sensitive embryonic systems like zebrafish cannot tolerate the off-target effects of siRNA knockdown but many Morpholino sequences give sufficiently specific knockdowns that they silence their target gene without otherwise messing up development.



Here's a Wikipedia page explaining the oligos in more detail: http://en.wikipedia.org/wiki/Morpholino



Here is a database of publications using Morpholinos: http://pubs.gene-tools.com


 
Nov 16, 2015
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Again thanks so much, this is a very interesting alternative to gene therapy.

A research came out a while ago about successful CEP290 gene therapy in the zebrafish. However, like in this case, it was performed in embryos, so that still doesn't tell us whether proper cilia can form in postnatal retinas following gene therapy or protein regulation...I guess we'll have to wait and see.
Thank you!
Fran